FIG 4.

Cytotoxicities of M. gallisepticum glp mutants when cultured with MRC-5 human lung fibroblasts. (Top and center) Wells of confluent MRC-5 cells stained with crystal violet after inoculation with M. gallisepticum strains in the presence (+) or absence (−) of glycerol. Cytotoxicity was determined by the presence or absence of a cytopathic effect on MRC-5 cells. One thousand M. gallisepticum cells were inoculated into 12-well plates with MRC-5 cells grown to confluence. No cytopathic effects were observed for any strain when grown in the presence of glucose instead of glycerol. (Bottom) Presence (+) or absence (−) of cytotoxicity for MRC-5 cells cultured alone or with M. gallisepticum strains.